1. Technical Field of the Invention
This invention relates to telecommunication systems and, more particularly, to a system and method of handling emergency calls from roaming mobile stations in a radio telecommunications network.
2. Description of Related Art
When a mobile subscriber initiates an emergency call such as a 911 call, the call is connected through a serving mobile switching center (MSC) to an end office (EO) known as a Public Safety Answering Point (PSAP). There may be situations in which the call is then prematurely disconnected. This disconnection may be due to the subscriber hanging up, loss of radio signal, border rescan problems, loss of the subscriber's mobile station (MS) during an attack, or other reasons. Current and previous versions of TR45.2 (PN 3581) state that under these circumstances, the serving MSC attempts to reestablish the call. In other words, the serving MSC pages for the MS, and if a page response is received, an alert signal is sent to the responding MS. If the alert signal is answered, the call is reconnected to the PSAP.
However, in existing networks, it is currently not possible to reconnect the emergency MS under certain circumstances. For example, the emergency MS may immediately originate another call to a different destination before the emergency call can be reconnected to the PSAP. Also, the MS may have been operating near the border of the serving MSC when the emergency call was dropped, and by the time the serving MSC attempts to reestablish the call the MS may have travelled into a bordering MSC. In this case, the emergency call cannot be reestablished.
There are no known prior art teachings of a solution to the aforementioned deficiency and shortcoming. In order to overcome the disadvantage of existing solutions, it would be advantageous to have a system and method of handling emergency calls in a radio telecommunications network in which an emergency MS is reconnected to the PSAP following a premature disconnection. The invention would reconnect the call to the PSAP even if the emergency MS attempts to originate a different call, or if the emergency MS has travelled into the service area of a bordering MSC.